Fuel System Basics

Tips, Tricks, And Knowledge For The Entry-Level Racer

The weekly racer faces some very real challenges with fuel systems. These problems are manifest in trying to make a fuel system that was designed for passenger cars feed an engine living in a racing environment. Even slight modifications, such as improved airflow through the use of a larger carburetor, the addition of improved exhaust, and ignition systems will enable an engine that has very limited internal modifications to develop more power, have an expanded rpm range and, subsequently, a greater need for fuel to supply these even limited modifications.

Engines for the weekly racer can range from a bone stock motor complete with air cleaner and mufflers to a highly tuned 500- to 600hp engine with very specialized fuel system needs. The weekly racer also has to deal with a variety of fuels, ranging from pump gasoline, E85, or race gas and, at the outer limits of the fuel spectrum, alcohol. All of these factors dictate the complexity of the fuel system. The amount of load that system will have to bear varies greatly.

For the most part, the weekly racer running at the local bullring will have a fuel system that is just a warmed over OEM system. Many of these race cars began life as daily drivers, never designed to be consistently driven at or near maximum power levels. Since the needs of the racer are so much different, stock fuel systems must be modified and improved to sustain the power requirements.

A typical short track fuel system is fairly simple. It includes a fuel tank or possibly a fuel cell, fuel lines, a fuel filter or two, and a fuel pump. If electronic fuel injection is being used, the system will also include fuel injectors and a computer. If the fuel system is supplying a high-power engine, the use of a fuel pressure regulator is almost a certainty, which may include a return line to the fuel tank. In those cases, you have fuel traveling from the tank to the engine and a line to route fuel that is bypassed from the regulator back to the tank. It boils down to a simple equation: The more power the engine produces the more complex the fuel system.

Buying Fuel
Regardless of the system’s complexity, it all begins with the point where you, the racer, buy your race fuel. This is a critical point in the fuel system that’s often never given a second consideration, but it’s just as important as any part of the fuel system on the car. It’s at this point that racers begin to really control the fuel system, and we all know that racing is all about control.

The simple action of transferring the fuel from the point of sale to the race car can and does contribute to variation in the fuel system. The fuel may only be exposed to one or possibly two containers between the point of sale and the race car. Devices such as funnels and fill lines that may be dirty or have been exposed to water, or through the mixing of old fuel and new fuel will contaminate fresh fuel.

The key is to treat your race fuel like you would treat the fuel that you put in your body. Keep it clean; make sure the containers you transfer fuel in are clean on the inside and the outside. Keep the fuel from becoming exposed to light and keep it cool.

Storage
Aside from the hopefully obvious safety aspects, poor fuel transportation and storage techniques can effectively take away some of the power producing components of the fuel. And I can think of very few racers who feel that they have too much power.

For example, everybody enjoys a sunny day but your race fuel likes dark and cool places and you should remember that. Fuel, especially gasoline, should always be stored in containers that do not allow the sunlight to reach the fuel. Most fuels are light sensitive and exposure to sunlight can and will damage the fuel. Prolonged exposure to sunlight can cause some race fuel to break down and some of the components to separate and once this happens it can’t be undone. You can’t just shake the container to mix the fuel components back together.

The containers should be either metal or an opaque plastic. If you’re using plastic fuel cans and you are transferring gasoline, the best color is black. Translucent white fuel containers may look cool and may be the rage, but they aren’t the best selection for the transportation and storage of fuel. You may be paying a price in diminished performance of the fuel for that cool look in the pits.

The translucent, white, or light-colored containers are fine for alcohol-based fuels. But remember that alcohol has its own set of idiosyncrasies. Alcohol is hydroscopic; it will absorb water from exposure to the air. Leave alcohol in a vented container in even a dry climate and it will absorb water and the water will degrade the power producing aspects of the fuel. All fuels should be shielded from the sunlight not just due to damage caused by ultraviolet light but the elevated temperatures that are caused by turning your fuel cans into solar heaters. Fuel containers stored in direct sunlight and even indirect sunlight will hiss as they are opened. This hissing is all of that high-dollar fuel venting its lighter elements into the atmosphere.

Try to avoid storing fuel in your trailer as this can be a real safety hazard. If you can smell high concentrations of fuel vapor in the trailer when you open the door you have two problems. The first problem is that the fuel jugs should not be venting into the atmosphere at all, fix that problem by purchasing fuel containers with closable vents. The second problem is that your trailer should be vented better so that fumes of any sort that do escape can’t gather in the trailer. The addition of some roof vents will help.

You need to remember that your fuel containers are really consumable items just like tires. They do not last forever and still wear out. If you’re using plastic fuel containers, inspect them regularly for cracks around the container and cap/vents. When you find a crack, replace the container. And even if you don’t and the container is several years old you should still replace it. If you are using metal containers you need to be on the lookout for rust in the can and around the fill points. Attention to small details is what separates the winners from the field fillers.

The majority of racers are unaware that many states have some very specific laws that govern the amount of fuel that can be carried in a vehicle outside of the tank. If you are going to transport fuel on the open road you need to be aware of the laws regarding the transporting of fuel.

Tanks & Cells
Once the fuel reaches the tank we still need to be very conscious about keeping the fuel clean. Fuel cells don’t last forever, the foam that’s inside the bladder can break down over the course of a season or sooner depending on the fuel you are running. Some race fuels are very unkind to synthetic rubber products over time. If this happens the fuel will be contaminated by the foam and can cause some real fuel system problems. The foam should be replaced at the intervals sug-gested by the fuel cell manufacturer.

If you are still using the OEM tank you are not home free just yet. It’s entirely possible that the tank has seen a good number of over the road miles and is possibly or more than likely contaminated with rust and scale after many years of use as a grocery getter. You may want to remove the tank and have it cleaned. The truth of the matter is that once the OEM tank is removed you might as well think about installing a fuel cell just for the safety that this type of tank offers.

Lines
Getting the fuel from the cell or tank is accomplished with the fuel lines. If you’re utilizing the OEM fuel lines, they’re usually made up of a combination of hard lines made of steel or flexible steel lines and rubber or neoprene hoses. Steel lines are usually very durable. The caution point, if you’re racing in a Street Stock-type of class, the OEM fuel lines, while very durable, are not designed for race cars. The elevated level of maintenance racers perform may cause wear and tear on the various components of the fuel lines, especially the fittings and threaded joints. You need to make sure that the fuel lines are routed in such a way that they are securely mounted to the chassis and are protected from any debris or errant broken part you may encounter on the track. If you have rerouted the fuel lines you need to make sure that the fuel line will not be in the way of any suspension parts that at their full range of movement could impact or rub on the fuel line. If you’re running the fuel lines through the passenger compartment, most racing organizations require that the line be run through a section of steel tubing that will isolate the fuel line from leaking into the driver’s compartment.

Pumps
In order to get the fuel through the lines, most circle track race cars utilize an engine-mounted pump of some type. It may be located on the engine in the OEM position or it could be a beltdriven pump on the front of the engine or even an engine-mounted pump driven off the camshaft. It may take the form of a diaphragm, piston, or a gear-type pump. The amount of power the engine generates will dictate the type of pump utilized.

It’s a fairly simple equation: The more power that the engine generates, the higher the need for a higher volume of fuel required. These types of high-volume pumps are usually found on engines running alcohol or very high horsepower gasoline engines. Some racers have opted to remove the mechanical fuel pumps and use electric pumps.

However, not all sanctioning bodies allow electric pumps. Due to the potential of the car being involved in a crash, the potential for fire is increased if a fuel line is damaged and the pump continues to run. While a very specific set of circumstances have to occur for this to play out, the risk is there and some racing organizations aren’t willing to take that risk. Even so, there are many race cars racing safely that are using electric fuel pumps.

Filter
You naturally need a filter for all this fuel traveling to the motor, but do we want the filter between the pump and the tank or between the pump and the carburetor? Filters placed between the pump and the tank, allow the use of larger filters in line. Mounting them to the chassis where they’re out of the way makes them potentially more difficult to service. Or we can place the filter between the pump and the carburetor. This option has some advantages, such as making it easier to work on and if it’s easier to work on, odds are that it will get serviced more often. Is there any one method that’s better between the two options? Can’t say for sure, but if you have a limit to the amount of fuel you can carry, placing the filter(s) between the tank and the pump allows you to use a larger filter to gain some fuel capacity.

However, nothing says you can’t do both. Place filters between the tank and the pump that have a larger media that may not be as restrictive and use a filter between the pump and the carburetor that has a much finer media that captures smaller particles that may be in your fuel. Another advantage of placing a filter in front of the pump is that it keeps debris from possibly damaging the pump, especially if you’re using a positive displacement mechanical pump that uses gears as opposed to a diaphragm-type of pump. If you have a high-dollar fuel pump, you will want to prevent any sort of debris from making it from the tank to the pump, possibly damaging the pump.

Regulator
The next thing we need to consider is the pressure of the fuel at the carburetor. With an engine that is closer to the power levels of the OEM engine, fuel pressure is less of a concern than with a highly tuned engine. Along with a pressure regulator you’ll also need a fuel-pressure gauge. Using a fuel-pressure gauge will allow you to measure the fuel pressure. The regulator needs to be mounted between the pump and the carburetor and depending on the type of regulator you may need to run a return line to the tank. The pressure gauge is one tool that you can’t do without if you’re running a fuel pressure regulator. With the gauge you’ll always know the exact pressure you’re getting at the carb. Remember, delivering too much fuel can cause just as many problems as not enough fuel. Being able to measure your fuel pressure gives you one more parameter to help you tune the car.

The gauge should be able to be read from inside the car while it’s at speed. With that said, in the interest of safety, try to utilize a fuel-pressure gauge that utilizes an electronic sending unit so you don’t have to run a fuel line into the driver’s compartment.

Conclusion
There are no magical or mystical things about fuel systems. The components are easy to understand and the execution of constructing a good fuel system is something that is easily accomplished. A well-engineered fuel system is just that, a system for delivering winning performance and dependable operation in all racing situations.

We’ve Temporarily Removed Comments

As part of our ongoing efforts to make HotRod.com better, faster, and easier for you to use, we’ve temporarily removed comments as well as the ability to comment. We’re testing and reviewing options to possibly bring comments back. As always, thanks for reading HotRod.com.